The present disclosure relates to rotary power tools, by way of example and not limitation, to a cordless driver used to install fasteners. More particularly, the present disclosure relates to a planetary gear train for use in power tools.
In accordance with the present disclosure, a planetary gear train is provided for use within a power tool, such as a cordless screwdriver. The planetary gear train comprises a ring gear housing adapted to be coupled to an output shaft designed to accept driver bits. The planetary gear train also includes a series of planetary gears pivotally coupled to a planetary gear carrier that is positioned within the ring gear housing. Rotation of a sun gear coupled to an electric motor rotates the planetary gears, which, in turn, rotates a first gear carrier.
In illustrative embodiments, the planetary gear train includes a centering ring positioned within the ring gear housing. The planetary gear carrier is adapted to be positioned within the centering ring. The centering ring is adapted to prevent the planetary gear carrier from shifting in a direction that is perpendicular to the axis of rotation of the gear train when an excessive amount of torque is applied to the output shaft of the power tool. During normal usage, the centering ring is designed to move freely or float within the ring gear to reduce driveline friction. In portable power tools where gear trains might be made from plastics material, the centering ring prevents distortion of the ring gear and the planetary gear carrier to minimize the amount of torque applied to individual gear teeth caused by gear train offset.
Additional features of the disclosure will become apparent to those skilled in the art upon consideration of the following detailed description of illustrative embodiments exemplifying the best mode of carrying out the disclosure as presently perceived.